In Japan, laughing loudly with an open mouth is considered impolite
TRUE - When they can't hold back a chuckle, locals usually hold a hand over their mouth
In UK, it's offensive to show two fingers with the palm of your hand facing towards you
TRUE - making a 'V' shape using your index and middle finger with the back of your hand facing someone is offensive in UK, Australia, New Zealand, South Africa
In the USA, you might offend waiters by raising your hand when they walk by you
FALSE - It's actually considered the best option. Calling out their names or whistling is bad manners